Research Of GaN-base Green Light Emitting Diodes With Insert Layer And The Ideality Factor Of GaN-base Light Emitting Diodes On SiC Substrates

In recent years, technical progress in the field of light-emitting diodes (LEDs) have been breathtaking. State of the art LEDs are small, rugged, reliable, bright, and efficient. In contrast to many other light sources, LEDs have the potential of converting electricity to light with near-unit efficiency. At present LEDs play an increasingly important role in a myriad of applications. GaN blue and green LEDs are developing rapidly as the main force of semiconductor solid-state lighting. But, there are more In components in the green LEDs quantum well and this lead to the larger polarization. This is the reason why green LEDs have lower efficient compared with blue LEDs. People often improve process for device performance in practice. The analysis about characteristics of devices is not well. And the mechanism related the performance of devices is not clear. In addition, GaN growth on the SiC substrates has many unique advantages and SiC substrates has gradually become a research focus in semiconductor materials. Considering of the progress of current research and laboratory conditions, in this thesis we did the following investigation.(1) We have grown InGaN/GaN multiquantum-well green light-emitting diodes on C-Al2O3substrates by MOCVD system and fabricated the device. At20mA current, the center wavelength is506nm.The In components of InGaN wells area are controlled by growth temperature. We calculated the In components of the sample according to XRD test and the result is23%. The blue shift and red shift phenomenon are found in the variable temperatures EL. In the EL of variable currents (20mA-350mA), the blue shift of center wavelength can be found and we attribute it to the effect of electric field caused by injected carriers.(2) We try to insert a low temperature GaN between on MQWs and n-GaN layer on the basic of conventional structure green LEDs for adjusting stress. The blue shift is smaller than conventional structure green LEDs. Through the analysis of test results, we conclude that the use of low temperature GaN layer adjust the stress between MQWs and n-GaN layer.(3) We have grown InGaN/GaN multiquantum-well blue light-emitting diodes on6H-SiC substrates by MOCVD system and fabricated the device with level electrode. At20mA current, the forward voltage is3.5V and the wavelength is452nm.The ideality factor of GaN LED on SiC substrates is7.8at the room temperature by I-V characteristic of the sample. The origin of the high diode-ideality factors in GaN LEDs on SiC substrates light-emitting diodes have analyzed. We have studied characteristics of various ideality factors over different temperature.